The present invention relates to an electron spin resonance (ESR) measurement method and a measurement device for detecting free radials in large samples. More particularly, the present invention relates to a method of measuring ESR in samples outside a resonator using the alternating magnetic field (B1) leaking to the exterior from the end of the resonator, and to an ESR device in which a resonator, a main electromagnet, and a field modulation coil are integrated to implement this method.
Free radicals are known to induce or aggravate a variety of diseases such as cancer, acute inflammation, ulcers, and myocardial infarction. Accordingly, it is anticipated that it will be possible to apply the in vivo detection of free radicals to the establishment of methods of diagnosing, treating, and preventing diseases relating to free radicals.
Previous ESR methods are known to be good methods of nondestructively detecting with high sensitivity the unpaired electrons of free radicals within substances. Further, it is possible to read a variety of information about a substance from changes in, and the range of, fluctuation of the Larmor precession frequency in the field of unpaired electrons. Measuring ESR in vivo requires the measurement at ordinary temperature of a high-volume, high dielectric loss sample in the form of an organism. However, in previous ESR, the sample insertion space of the resonator, which is the detection element, is small and the resonant frequency (about 9.5 GHz) is the high dielectric loss band of water, precluding in vivo measurement.
Accordingly, the methods of lowering the frequency to decrease the dielectric loss and increasing the size of the resonator to widen the sample insertion space have been adopted. However, the resonators that have been fabricated thus far have been limited to a size permitting the insertion of small experimental animals; no device permitting practical use has been developed.
Methods of observing the free radicals on the surface of a large sample such as an organism by using a resonator as a probe head are also being examined. The use of parallel components of B1 as a plane constituting part of the loop of the resonator, permitting the positioning of the main magnet and the field modulation coil on a plane parallel with the loop plane, and the use of an entire device of this type as a probe head to achieve size reduction and integration have been conceived (Patent Application Publication No. Hei 11-046076). In this method, ESR measurement of the surface of a large sample is possible, but deep measurement, that is, ESR measurement of the interior of the sample, is impossible.
In consideration of such problems of prior art, the present invention has for its object to provide an ESR measurement method and device capable of ESR measurement of the interior of large samples.
The present inventors conducted extensive research into achieving the above-stated objects, resulting in the discovery that it was possible to conduct ESR measurement of the interior of a sample positioned outside the resonator by employing the B1 leaking to the exterior from the end of the resonator, and that by employing a device integrating a resonator capable of supplying B1 to a sample located outside the resonator, and an electromagnet capable of supplying a static magnetic field (B0) and a modulation field via a modulation field coil, from the resonator side rather than from a plane contained within the end of the resonator, ESR measurement of the interior of a large sample was possible. The present invention was devised on the basis of this knowledge.
That is, the present invention provides a method of measuring ESR in a sample located outside a resonator using B1 leaking to the exterior from the end of the resonator. In a preferred mode of implementing the present invention, B1 are applied by the end of the resonator to a sample located outside the resonator, and using a magnet located on the resonator side of a plane containing the end of the resonator to apply B0 and a modulation field to the sample, the ESR of the sample is measured. Low-frequency microwaves to radiowaves are employed with preference as the ESR irradiation in the present invention.
The present invention further provides an ESR device comprised of at least a resonator capable of applying B1 leaking from the end of the resonator to a sample located outside the resonator, and a magnet located on the resonator side of a plane containing the end of the resonator that is capable of applying B0 and a modulation field. In the ESR device of the present invention, the resonator, main electromagnet, and field modulation coil are positioned on the resonator side of the plane containing the end of the resonator.